An experimental investigation of the recirculation zone of laminar flames stabilized on bluff bodies at low Reynolds numbers

Abstract

As part of a program to explain the shift in the maximum blowoff velocity from stoichiometric mixture ratio for small flame holder sizes, laminar flame stabilization studies v/ere made using cylindrical flame holders of 0. 031 to 0. 125 inches in diameter at Reynolds numbers 3 4 in the range of 10 to 10 . Chemical samples of the gases in the recirculation region behind the flame holders were taken and analyzed to determine the composition of the burning gases at the flame front. Maximum temperature measurements were taken of this same region. It was found that at these low Reynolds numbers, the composition was different than in the unburned approach mixtures, and that this was apparently due to the difference in molecular diffusion of the fuel and air across the flame front. The variation in the composition of the burning gases appears to be a direct function of the approach fuel-air mixture ratio for each diameter and approach mixture velocity.